1. Field of the Invention
The present invention relates to a resin panel in which a skin layer is formed on its surface and an expanded layer having a plurality of voids is formed therein. The invention also relates to an automobile door using the resin panel.
2. Description of Related Art
Japanese Unexamined Patent Publication No. H11-179751 discloses a molded resin body including a skin layer formed on its surface and an expanded layer having a plurality of voids formed therein. According to the literature, the molded resin body is obtained using a mold assembly which consists of a moving mold containing a movable mold inside and a stationary mold. Specifically, a fiber-filled thermoplastic resin is filled by injection in a cavity of the mold assembly in a closed state and the movable mold is retracted in the moving mold to increase the cavity volume in the course of solidification of the fiber-filled thermoplastic resin, thereby allowing the fiber-filled thermoplastic resin to expand. The molded resin body is in the form of a panel and the entire region of the panel is made of the expanded layer for weight reduction. The H 11-179751 literature also describes that integral convex parts are formed on the surface of the molded resin body and a layer harder than the expanded layer is formed in parts of the molded resin body corresponding to the convex parts so that the parts of the molded resin body around the convex parts are improved in strength and rigidity.
In some cases, the molded resin body is in the form of a flat panel and provided with integral attachment parts for fixing the panel to a target object. In this case, if the panel is configured as disclosed in the H11-179751 literature, the hard layer provided in the parts of the panel body corresponding to the attachment parts is still an expanded layer, though it is harder than the expanded layer in the other parts of the panel body. Therefore, the parts of the panel body around the attachment parts as well as the panel body itself may not provide adequate strength and rigidity. Worse still, torsional rigidity and bending rigidity may be insufficient. In such a situation, the resin panel cannot be fixed to the target object with stability.